North Columbia

Sunday is set to be great day to be in the mountains, with lots of new snow and weather clearing. Manage the inevitable euphoria with a constant reminder that the new snow needs time to settle and that storm slabs are primed for human triggering.

High -

Saturday night: Cloudy with tapering flurries bringing a final 2-5 cm of new snow. Strong northwest winds easing to light by morning.Sunday: A mix of sun and cloud with cloud decreasing over the day and isolated flurries leaving a trace of new snow. Light northeast winds. Alpine high temperatures around -12.Monday: A mix of sun and cloud. Light southwest winds. Alpine high temperatures around -11.Tuesday: Mainly cloudy. Light southwest winds. Alpine high temperatures reaching -4 as a mild alpine temperature inversion layer establishes toward evening.

Although we don't yet have reports from Saturday in the North Columbia region, neighbouring Glacier National Park saw several size 2 and numerous size 3 storm slab releases on many of their regularly performing avalanche paths. With similar but deeper conditions in much of the North Columbias, it's safe to assume that it was an active day for avalanches, whether natural or human-triggered. Prior to the storm, the last reported persistent slab activity was last Sunday when a few large (size 3) persistent slab avalanches were observed on south facing alpine features. This was the final report from a widespread persistent slab avalanche cycle that was quite active last week, particularly in the Selkirks and the northern tip of the Monashees.Looking forward, expect diminishing snowfall and wind to decrease natural avalanche activity while the potential for human triggering remains elevated. Although the likelihood of storm slabs 'stepping down' to deeper persistent slab problems is in question, travel plans should account for very large avalanches as the possible result.

Saturday's storm left about 30-40 cm of new snow on the surface. Below the new snow, 10 to 20 cm of older low density snow sits above old wind slabs in the alpine, and in some isolated areas above small surface hoar (feathery crystals).A weak layer that formed during the dry spell in early December is now 100 to 140 cm deep. The layer is composed of weak facets, surface hoar, and a sun crust on steep south-facing slopes. Although activity at this layer has greatly diminished over the last week, it remains a concern for the possibility of surface slabs acting as a trigger for 'step down' avalanches. The places of greatest concern for this type of avalanche will be north and east facing slopes between 1900-2300 m and steep south-facing slopes in the alpine.The lower snowpack is generally strong and settled, with a crust that formed in late October near the bottom of the snowpack.